Exhaust system for a small watercraft

ABSTRACT

An exhaust system for a small watercraft wherein exhaust gas can flow smoothly includes a water muffler in the exhaust system for an engine incorporated in a small watercraft. An exhaust pipe is connected to the water muffler extending upwardly once and then extending downwardly in such a manner as to have a substantially U-shape. Spiral baffle plates are provided for spirally introducing exhaust gas on an inner face of the U-shaped exhaust pipe. Since the baffle plates are provided on the exhaust pipe, cooling water and exhaust gas can be separated from each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present nonprovisional application claims priority under 35 USC 119to Japanese Patent Application No. 2002-193360 filed on Jul. 2, 2002 theentire contents thereof is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an exhaust system for a small watercraft thatis propeled with jet water jetted from a jet pump.

2. Description of Background Art

A personal watercraft is a watercraft wherein a jet pump is attached toa rear portion of a watercraft body and is driven by an engine to takein water from the bottom of the watercraft and jet the taken-in waterrearwardly to propel the watercraft.

A personal watercraft is known as set forth in Japanese Patent Laid-OpenNo. Hei 10-212936 entitled “Exhaust System for a Personal Watercraft.”Essential part of FIG. 1 of the Official Gazette for his patent isincorporated herein as FIG. 8 and a description is given below of theexhaust system for this personal watercraft.

FIG. 8 is a side elevational view showing the conventional smallwatercraft. The small watercraft 100 includes an engine 102 provided ata substantially central location of a watercraft body 101. A watermuffler 104 is connected to the engine 102 by an exhaust pipe 103, and asubstantially inverted U-shaped exhaust pipe 105 is provided for thewater muffler 104.

The substantially inverted U-shaped exhaust pipe 105 is connected at oneend thereof to the water muffler 104, and extends, at a substantiallyhalf portion 106 thereof adjacent the substantially inverted U-shapedexhaust pipe 105, upwardly once and then extends, at the remainingsubstantially half portion 107 thereof, downwardly such that itgenerally has a substantially U-shape.

With the substantially inverted U-shaped exhaust system, exhaust gas andcooling water having arrived at the inside of the water muffler 104 fromthe engine 102 side can be discharged to the outside through theU-shaped exhaust pipe 105.

However, since the cooling water and the exhaust gas in the watermuffler 104 flow in a mixed state into the exhaust pipe 105, the coolingwater flows through an overall sectional area in the inside of theexhaust pipe 105.

Where the cooling water flows through an overall sectional area in theinside of the exhaust pipe 105 in this manner, it is estimated that thecooling water may fill up the inside of the exhaust pipe 105 to disturba flow of the exhaust gas.

SUMMARY AND OBJECTS OF THE INVENTION

Therefore, it is an object of the present invention to provide anexhaust system for a small watercraft wherein exhaust gas can flowsmoothly.

In order to solve the subject described above, according to the presentinvention, an exhaust system for an engine incorporated in the smallwatercraft includes a water muffler wherein an exhaust pipe connected tothe water muffler extends upwardly once and then extends downwardly insuch a manner as to have a substantially U-shape and exhaust gas andcooling water in the water muffler are discharged to the outside throughthe U-shaped exhaust pipe. A spiral baffle plates is provided forspirally introducing the exhaust gas. The spiral baffle plates areprovided on an inner face of the U-shaped exhaust pipe.

Since the spiral baffle plates are provided on the inner face of theexhaust pipe, a flow of exhaust gas can be converted into a spiral flowby the baffle plates. Consequently, centrifugal force acts upon coolingwater having entering into the exhaust pipe together with the exhaustgas so that the cooling water can be drawn up to the inner face of theexhaust pipe.

Consequently, since the cooling water can flow along the inner face ofthe exhaust pipe while the exhaust gas flows along a central portion ofthe exhaust pipe, the cooling water and the exhaust gas can be separatedfrom each other.

According to the present invention, the exhaust system for a smallwatercraft includes an on/off valve capable of opening and closing anoutlet of the exhaust pipe that is provided at the outlet of the exhaustpipe.

The on/off valve is provided on the outlet side of the exhaust pipe suchthat the outlet of the exhaust pipe can be opened or closed with theon/off valve. Since the on/off valve is provided, admission of waterinto the exhaust pipe from the outlet side can be prevented.

Incidentally, where the on/off valve is provided on the outlet side ofthe exhaust pipe, it is considered that a support member that supportsthe on/off valve may cross the outlet of the exhaust pipe. In thisinstance, there is a possibility that, if cooling water and exhaust gasflow in a mixed state with each other in the exhaust pipe, then thecooling water may strike against the support member and may reside inthe proximity of the outlet of the exhaust pipe. Therefore, it maybeconsidered that the residing cooling water may have a bad influence onthe flow of the exhaust gas to disturb the flow of the exhaust gas.

Therefore, in the present invention, the exhaust system, is configuredsuch that the cooling water flows along the inner face of the exhaustpipe while the exhaust gas flows along a central portion of the exhaustpipe to separate the cooling water and the exhaust gas each other. Whenthe cooling water and the exhaust gas are separated from each other inthis manner, the cooling water striking against the support member canbe prevented from disturbing the flow of the exhaust gas.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a side elevational view of a small watercraft that includes anexhaust system according to the present invention;

FIG. 2 is a perspective view of the exhaust system for a smallwatercraft according to the present invention;

FIG. 3 is a schematic view of an essential part of the exhaust systemfor a small watercraft according to the present invention;

FIG. 4 is an enlarged view of an essential part of the exhaust systemfor a small watercraft according to the present invention;

FIG. 5 is a sectional view showing baffle plates of the exhaust systemfor a small watercraft according to the present invention;

FIGS. 6(a) and 6(b) are schematic views illustrating a first action ofthe exhaust system for a small watercraft according to the presentinvention;

FIGS. 7(a) and 7(b) are schematic views illustrating a second action ofthe exhaust system for a small watercraft according to the presentinvention; and

FIG. 8 is a side elevational view showing a conventional smallwatercraft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is described below with referenceto the accompanying drawings. It is to be noted that the drawings shouldbe viewed in the direction of reference characters.

FIG. 1 is a side elevational view of a small watercraft that includes anexhaust system according to the present invention.

The small watercraft 10 includes a fuel tank 14 attached to a frontportion 11 a of a watercraft body 11, an engine 15 is providedrearwardly of the fuel tank 14. A pump room 16 is provided rearwardly ofthe engine 15 with a jet pump 20 being provided in the pump room 16. Anexhaust system 30 is provided for a small watercraft attached at theintake side thereof to the engine 15 and attached at the exhaust sidethereof to the pump room 16. A steering handle bar 28 is attached abovethe fuel tank 14 and a seat 29 is attached rearwardly of the steeringhandle bar 28.

The jet pump 20 has a housing 21 extending rearwardly from an opening 13of a watercraft bottom 12, and an impeller 22 is mounted for rotation inthe housing 21 and connected to a drive shaft 23 of the engine 15.

With the jet pump 20, if the engine 15 is driven to rotate the impeller22, then water sucked in through the opening 13 of the watercraft bottom12 can be jetted rearwardly of the watercraft body 11 from a steeringnozzle 25 through a rear end opening of the housing 21 to propel thesmall watercraft 10.

The steering nozzle 25 is a member mounted for swinging movement inleftward and rightward directions at a rear end of the housing 21. Thesteering direction of the watercraft body 11 can be controlled byswinging the steering nozzle 25 in the leftward or rightward directionthrough an operation of the steering handle bar 28.

FIG. 2 is a perspective view of the exhaust system for a smallwatercraft according to the present invention.

The exhaust system 30 is configured such that a water muffler 32 isconnected to the engine 15 through an exhaust box 31 and an exhaust pipe33 is connected to the water muffler 32. A resonator 34 is connected tothe exhaust pipe 33 and an on/off valve 35 is provided for the resonator34.

More particularly, the exhaust box 31 is connected through an exhaustpipe 36 to the engine 15 incorporated in the small watercraft 10, andthe exhaust box 31 is connected to the water muffler 32 through aconnecting pipe 37.

The exhaust pipe 33 is connected at an inlet side end 33 a thereof tothe water muffler 32 and has a substantially U-shape such that itextends upwardly once and then extends downwardly, and an outlet sideend 33 b of the exhaust pipe 33 extends through a ceiling wall 17 of thepump room 16.

FIG. 3 is a schematic view of an essential part of the exhaust systemfor a small watercraft according to the present invention.

The exhaust pipe 33 includes an inlet side pipe 41 which forms the inletside end 33 a, an outlet side pipe 42 which forms the outlet side end 33b. A substantially inverted U-shaped hose 43 extends through the outletside pipe 42 and the inlet side pipe 41.

In particular, the exhaust pipe 33 is configured such that the inletside pipe 41 is inserted in the water muffler 32 and the outlet sidepipe 42 extends through the ceiling wall 17 of the pump room 16. A rearend 43 a of the hose 43 is in communication with the outlet side pipe 42and a front end 43 b is in communication with the inlet side pipe 41such that the exhaust pipe 33 is formed in a substantially invertedU-shape while the rear end 43 a is attached to the outlet side pipe 42with a rear end band 44 and the front end 43 b is attached to the inletside pipe 41 with a front end band 45.

In the U-shaped exhaust pipe 33, a plurality of spiral baffle plates 46. . . for spirally introducing exhaust gas are provided on an inner face43 c of the front end 43 b of the hose 43, that is, on the inner face ofthe U-shaped exhaust pipe.

FIG. 4 is an enlarged view of essential part of the exhaust system for asmall watercraft according to the present invention and shows a statewherein a heat shield plate 19 is attached to a rear face of the ceilingwall 17 of the pump room 16 and the resonator 34 is provided on the backface side of the heat shield plate 19, and the outlet side pipe 42 isinserted in a mount hole 17 a of the ceiling wall 17 of the pump room16. A packing 47 is provided on an upper wall 34 a of the resonator 34and the outlet side pipe 42 is fitted in the packing 47 such that theoutlet side pipe 42 is exposed to the inside of the resonator 34.

Further, FIG. 4 illustrates first and second openings 38 and 39 that areprovided on a bottom wall 34 b of the resonator 34 opposing to theoutlet side pipe 42 and are exposed to an internal space 18 of the pumproom 16. A support beam 40 is provided between the first and secondopenings 38 and 39 and is formed so as to have a substantially invertedV-shaped cross section such that a apex portion 40 a thereof projectstoward the outlet side pipe 42 while the on/off valve 35 is attached tothe support beam 40.

The on/off valve 35 is configured such that a substantially invertedL-shaped bracket 51 is fastened to the support beam 40 by means ofscrews 52 . . . to sandwich a substantially central portion of a valvebody 53 between the bracket 51 and the support beam 40.

The valve body 53 includes first and second flaps 54 and 55. The firstflap 54 hangs downwardly with its weight but assumes an inclined stateas it is supported by an inclined portion 51 a of the bracket 51.Because of its weight, the second flap 55 hangs downwardly substantiallyvertically as seen in FIG. 4.

Consequently, the first and second openings 38 and 39 of the resonator34 can be kept in an open state.

By providing the on/off valve 35 on the outlet 42 b side of the outletside pipe 42 (on the outlet side of the exhaust pipe 33) in this manner,the first and second openings 38 and 39 of the resonator 34 can beopened or closed with the on/off valve 35 to open or close the outlet 42b of the outlet side pipe 42.

Here, if the small watercraft 10 during operation should be reversed,then the first flap 54 moves to the bottom wall 34 b of the resonator 34with the weight of the first flap 54 itself to close the first opening38 of the resonator 34. Simultaneously, the second flap 55 moves to thebottom wall 34 b of the resonator 34 with the weight of the second flap55 itself to close the second opening 39 of the resonator 34.

By closing the first and second openings 38 and 39 in this manner,admission of water into the exhaust pipe 33 can be prevented.

FIG. 5 is a sectional view showing baffle plates of the exhaust systemfor a small watercraft according to the present invention and showing astate wherein the spiral baffle plates 46 . . . for spirally introducingexhaust gas within a range L are provided at fixed intervals S with anangle of inclination θ on the inner face 43 c of the front end 43 b ofthe hose 43 (on the inner face of the U-shaped exhaust pipe 33).

Each of the baffle plates 46 . . . is formed such that it has asectional shape like an isosceles triangle and the bottom side of theisosceles triangle is provided on the inner face 43 c of the hose 43such that the center thereof projects like an edge line so that the edgeline has a height H.

It is to be noted that the cross sectional shape of the baffle plates 46. . . is limited to this, but may be, for example, a rectangular shape.

Further, while a description is given above of the example wherein thebaffle plates 46 . . . are provided within a range L on the inner face43 c of the front end 43 b, the range L can be set arbitrarily. Forexample, it is possible to set the range L so as to be equal to theoverall length of the hose 43.

Furthermore, also it is possible to integrally mold the baffle plates 46. . . with the hose 43 when the hose 43 is molded, or it is alsopossible to adhere the baffle plates 46 . . . to the inner face 43 c ofthe hose 43.

Since the spiral baffle plates 46 . . . are provided on the inner face43 c of the exhaust pipe 33, a flow of exhaust gas can be introducedspirally by the baffle plates 46 . . . . Consequently, centrifugal forceacts upon cooling water having advanced into the exhaust pipe togetherwith exhaust gas so that it is drawn up to the inner face 43 c of theexhaust pipe 33.

Consequently, the cooling water can flow along the inner face 43 c ofthe exhaust pipe 33 while the exhaust gas flows along a central portion43 d of the exhaust pipe 33, and therefore, the cooling water and theexhaust gas can be separated from each other.

As a result, exhaust gas in the exhaust pipe 33 can flow smoothly whilea flow of the exhaust gas is not disturbed by cooling water.

Subsequently, an action of the exhaust system for a small watercraft isdescribed with reference to FIGS. 6(a) and 6(b) and to FIGS. 7(a) and7(b).

FIGS. 6(a) and (b) are views illustrating a first action of the exhaustsystem for a small watercraft according to the present invention.

Referring to FIG. 6(a), exhaust gas passes through the exhaust box 31and the connecting pipe 37 and enters into the water muffler 32 asindicated by an arrow mark 1 inside a circle. Consequently, the enteringexhaust gas is mixed with cooling water 57 in the water muffler 32.

The cooling water 57 and the exhaust gas mixed in the water muffler 32enter into the inlet side; pipe 41 of the exhaust pipe 33 as indicatedby an arrow mark 2 inside a circle.

Referring to FIG. 6(b), the cooling water 57 and the exhaust gas havingentered the inlet side pipe 41 enter into the hose 43. Since the spiralbaffle plates 46 are provided on the inner face 43 c of the front end 43b of the hose 43, the flow of the exhaust gas can be converted into aspiral flow as indicated by an arrow mark 3 inside a circle by thebaffle plates 46 . . .

Consequently, centrifugal force acts upon the cooling water 57 havingentered into the exhaust pipe 33 together with the exhaust gas, andtherefore, the cooling water 57 can be drawn up to the inner face 43 cof the exhaust pipe 33.

Therefore, since the cooling water 57 can flow along the inner face 43 cof the exhaust pipe 33 while the exhaust gas flows along the centralportion 43 d of the exhaust pipe 33, the cooling water 57 and theexhaust gas can be separated from each other.

FIGS. 7(a) and 7(b) are views illustrating a second action of theexhaust system for a small watercraft according to the presentinvention.

Referring to FIG. 7(a), exhaust gas having passed the spiral baffleplates 46 . . . flow spirally in the hose 43.

Consequently, the cooling water 57 flows along the inner face 43 c ofthe exhaust pipe 33 up to the rear end 43 a of the hose 43 while theexhaust gas flows along the central portion 43 d of the hose 43 asindicated by an arrow mark 4 inside a circle, and therefore, the coolingwater and the exhaust gas can be separated from each other.

Referring to FIG. 7(b), the exhaust gas having arrived at the rear end43 a of the hose 43 flows along the central portion 43 d of the outletside pipe 42 and flows from the outlet 42 b of the outlet side pipe 42through the first and second openings 38 and 39 of the resonator 34 tothe outside as indicated by arrow marks 5 inside a circle.

Meanwhile, the cooling water 57 having reached the rear end 43 a of thehose 43 flows along an inner face 42 a of the outlet side pipe 42 andthen flows from the outlet 42 b of the outlet side pipe 42 through thefirst and second openings 38 and 39 of the resonator 34 to the outsideas indicated by the arrow marks 5 inside a circle similarly to theexhaust gas.

Since the exhaust gas can flow in a state separated from the coolingwater 57 in this manner, the exhaust gas in the exhaust pipe 33 can flowsmoothly while the flow of the exhaust gas is not disturbed by thecooling water 57.

Furthermore, while the support beam 40 which supports the on/off valve35 extends such that it crosses the outlet 42 b of the outlet side pipe42, since the support beam 40 is formed in a substantially invertedV-shape and the apex portion 40 a thereof projects in a tapering mannerinto the resonator 34, the cooling water 57 and the exhaust gas can bedischarged efficiently.

Further, since the cooling water 57 flows along the inner face of theexhaust pipe 33 (principally along the inner face 43 c of the hose 43)and the exhaust gas flows along the central portion of the exhaust pipe33 (principally along the central portion 43 d of the hose 43) as shownin FIG. 7(a), the cooling water and the exhaust gas can be separatedfrom each other. Consequently, even if the support beam 40 for theon/off valve 35 is provided on the outlet side of the exhaust pipe 33,it does not disturb the flow of the exhaust gas and allows the exhaustgas to flow smoothly.

It is to be noted that, while the embodiment described above is anexample wherein the baffle plates 46 . . . are provided at the front end43 b of the hose 43 which forms the exhaust pipe 33, the location of thebaffle plates 46 . . . is not limited to this, but the spiral baffleplates 46 . . . may otherwise be provided in the inlet side pipe 41 orthe outlet side pipe 42 of the exhaust pipe 33.

Further, while description is given above of an example wherein the hose43 is used for the exhaust pipe 33, a tube may be used in place of thehose 43.

Furthermore, while the embodiment described above is an example whereinthe resonator 34 is provided on the outlet side end 33 b of the exhaustpipe 33, the present invention is not limited to this, but may beapplied to another exhaust system that does not include the resonator34.

Further, while the embodiment described above is an example wherein theon/off valve 35 is provided for the resonator 34, the present inventionis not limited to this but can be applied to another exhaust systemwhich does not include the on/off valve 35.

The present invention exhibits the following effects due to theconfiguration described above.

According to the present invention, since the spiral baffle plates areprovided on the inner face of the exhaust pipe, a flow of exhaust gascan be converted into a spiral flow by the baffle plates. Consequently,centrifugal force acts upon cooling water having entered into theexhaust pipe together with the exhaust gas so that the cooling water canbe drawn up to the inner face of the exhaust pipe.

Consequently, since the cooling water can flow along the inner face ofthe exhaust pipe while the exhaust gas flows along a central portion ofthe exhaust pipe, the cooling water and the exhaust gas can be separatedfrom each other. Accordingly, the exhaust gas in the exhaust pipe canflow smoothly while the flow of exhaust gas is not disturbed by thecooling water.

According to the present invention, the on/off valve is provided on theoutlet side of the exhaust pipe such that the outlet of the exhaust pipecan be opened or closed with the on/off valve. Since the on/off valve isprovided, admission of water into the exhaust pipe from the outlet sidecan be prevented.

In addition, since the cooling water and the exhaust gas can beseparated from each other as the cooling water flows along the innerface of the exhaust pipe while the exhaust gas flows along a centralportion of the exhaust pipe, even where a support member for the on/offvalve is provided on the outlet side of the exhaust pipe, the exhaustgas can flow smoothly while the flow of the exhaust gas is not disturbedby the cooling water having struck against the support member.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An exhaust system for an engine of a smallwatercraft includes a water muffler and wherein an exhaust pipeconnected to said water muffler extends upwardly once and then extendsdownwardly in such a manner as to have a substantially U-shape andexhaust gas and cooling water in said water muffler are discharged tothe outside through said U-shaped exhaust pipe comprising: spiral baffleplates for spirally introducing exhaust gas being provided on an innerface of said U-shaped exhaust pipe.
 2. The exhaust system for a smallwatercraft according to claim 1, wherein an on/off valve capable ofopening and closing an outlet of said exhaust pipe is provided at theoutlet of said exhaust pipe.
 3. The exhaust system for a smallwatercraft according to claim 1, wherein the spiral baffle plates extendalong the inner face of said U-shaped exhaust pipe for a predeterminedinterval.
 4. The exhaust system for a small watercraft according toclaim 3, wherein said spiral baffle plates are spaced apart by apredetermine interval and are inclined relative to a longitudinal axisby a predetermined angle.
 5. The exhaust system for a small watercraftaccording to claim 1, wherein the baffle plates have a sectional shapein the form of an isosceles triangle.
 6. The exhaust system for a smallwatercraft according to claim 1, and further including a resonatoroperatively connected to the exhaust pipe, said resonator including atleast one discharge opening being disposed therein, an on/off valvebeing mounted relative to said at least one discharge opening forselectively closing said at least one discharge opening.
 7. The exhaustsystem for a small watercraft according to claim 6, wherein saidresonator includes two discharge openings and said on/off valve isoperatively positioned adjacent to said two discharge openings forselectively closing said at least two discharge openings.
 8. The exhaustsystem for a small watercraft according to claim 7, wherein said on/offvalve includes a first flap having a predetermined weight and a secondflap having a predetermined weight and wherein if the watercraft turnsover the predetermined weight of the first and second flaps closes thefirst and second openings in said resonator.
 9. The exhaust system for asmall watercraft according to claim 1, wherein the spiral baffle platesare integrally molded on the inner face of the U-shaped exhaust pipe.10. An exhaust system adapted to be used with an engine of a watercraftcomprising: an exhaust pipe adapted to be connected to a water muffler,said exhaust pipe including an inner face; spiral baffle plates forspirally introducing exhaust gas, said spiral baffle plates beingprovided on said inner face of said exhaust pipe.
 11. The exhaust systemaccording to claim 10, wherein said exhaust pipe extends upwardly onceand then extends downwardly in such a manner as to have a substantiallyU-shape and exhaust gas and cooling water in said water muffler aredischarged to the outside through said U-shaped exhaust pipe.
 12. Theexhaust system according to claim 10, wherein an on/off valve capable ofopening and closing an outlet of said exhaust pipe is provided at theoutlet of said exhaust pipe.
 13. The exhaust system according to claim10, wherein the spiral baffle plates extend along the inner face of saidU-shaped exhaust pipe for a predetermined interval.
 14. The exhaustsystem according to claim 13, wherein said spiral baffle plates arespaced apart by a predetermine interval and are inclined relative to alongitudinal axis by a predetermined angle.
 15. The exhaust systemaccording to claim 10, wherein the baffle plates have a sectional shapein the form of an isosceles triangle.
 16. The exhaust system accordingto claim 10, and further including a resonator operatively connected tothe exhaust pipe, said resonator including at least one dischargeopening being disposed therein, an on/off valve being mounted relativeto said at least one discharge opening for selectively closing said atleast one discharge opening.
 17. The exhaust system according to claim16, wherein said resonator includes two discharge openings and saidon/off valve is operatively positioned adjacent to said two dischargeopenings for selectively closing said at least two discharge openings.18. The exhaust system according to claim 17, wherein said on/off valveincludes a first flap having a predetermined weight and a second flaphaving a predetermined weight and wherein if the exhaust system turnsover the predetermined weight of the first and second flaps closes thefirst and second openings in said resonator.
 19. The exhaust systemaccording to claim 10, wherein the spiral baffle plates are integrallymolded on the inner face of the U-shaped exhaust pipe.